The present invention relates to a bearing support of a throttle valve shaft in the housing of an exhaust gas line in which the shaft is rotatably supported on both sides in one cup-shaped bearing sleeve element and in which the housing is constructed conically within the areas of the bearing sleeve elements whereby the interior cross-sectional surface of the housing within the area of a bearing sleeve element and the external cross-sectional surface of the latter taper in the same direction.
With such a bearing support, used in series-produced vehicles of the assignee of the present application, by means of which slight shaft bendings and minimum axial offsets of the bearings can be automatically compensated, a bearing sleeve element is retained against the housing by means of an axially acting compression spring. The same spring is simultaneously supported also at a spring plate which is securely connected with the throttle valve shaft. The axially acting spring force is therewith further transmitted by way of the shaft to the oppositely disposed bearing, as a result of which the latter is also retained against the housing. This "inner stressing" of the shaft, however, leads to the fact that larger friction forces may occur between this bearing sleeve element and the components retaining the same against the housing (spring plate, respectively, on the other side an axially fixed disk) during an actuation of the throttle valve. As a result thereof, relatively high actuating forces are required for the rotation of the throttle valve shaft.
The present invention is therefore concerned with the task to provide a bearing support of the type described hereinabove in which the forces necessary for the actuation of the throttle valve shaft are kept to a minimum.
The underlying problems are solved according to the present invention in that each bearing sleeve element is retained by itself against the housing by means of a spring supported at the housing and in that the shaft is secured against axial displacement by means of a separate axial bearing.
Due to the fact that the two springs retaining the bearing sleeve elements against the housing are supported directly at the housing, no bearing-conditioned or stress-conditioned axial forces act any longer on the shaft itself so that during the actuation of the shaft, no increased friction forces have to be overcome any longer, whereby the provided separate axial bearing generally precludes a displacement of the shaft in case of eventually occurring minimum axial forces during an actuation of the throttle valve.
A particularly simple and therewith also cost-favorable construction of the axial bearing is obtained in accordance with the present invention if the axial bearing is formed of two retaining rings axially fixed on the shaft which are abuttingly disposed to both sides of a pressure plate fixedly connected with the housing and absorbing the spring force.